(HealthDay News) – For girls receiving two vs. three doses of human papillomavirus (HPV) vaccine, antibody responses to HPV-16 and HPV-18 are non-inferior one month after the last dose, according to a study published in the May 1 issue of the Journal of the American Medical Association, a theme issue on child health.
Simon R.M. Dobson, MD, from the University of British Columbia in Vancouver, Canada, and colleagues conducted a phase 3 randomized multicenter immunogenicity study involving 830 Canadian females to determine whether mean antibody levels to HPV-16 and HPV-18 were non-inferior for those receiving two vs. three doses of HPV vaccine within six months. Nine- to 13-year-old girls were randomized to receive three or two doses (261 and 259, respectively). An additional 310 young women (aged 16–26 years) received three doses.
At one month after the last dose, the researchers found that the geometric mean titers for HPV-16 and HPV-18 were non-inferior for girls receiving two doses compared to women and girls receiving three doses. For all genotypes, the geometric mean titers remained non-inferior at 36 months for girls receiving two doses compared to women receiving three doses. For girls receiving two doses vs. three doses, antibody responses were non-inferior for all vaccine genotypes at month seven, but not for HPV-18 by month 24 or for HPV-6 by month 36.
“There is a balance to be found between the incremental value of an additional dose on population effectiveness and the opportunity costs of using the resources required for the extra dose in other public health programs,” the authors write. “This is especially the case for HPV vaccines at their present cost.”
Several authors disclosed financial ties to pharmaceutical companies, including Merck, which conducted the antibody assays at no cost.